This invention relates generally to rotatable irrigation sprinklers particularly of the type including a reaction drive member for interacting cyclically with a projected water stream to rotate the sprinkler in steps and thereby alter the azimuthal direction of the water stream. More specifically, this invention relates to an improved drive assembly for a reaction drive sprinkler of the general type disclosed and claimed in U.S. Pat. No. 4,434,937.
Rotatable water sprinklers of the so-called reaction drive type are known in the art for supplying irrigation water over a substantial surface area to irrigate lawns, crops, and the like. Such reaction drive sprinklers typically comprise a sprinkler body supported by a bearing assembly for rotation about the upper end of a water supply standpipe. Irrigation water under pressure supplied through the standpipe flows upwardly through the sprinkler body and is discharged outwardly through a discharge outlet or nozzle with a selected angle or upward inclination. A reaction drive arm is mounted on the sprinkler body for pivoting movement typically within a generally vertical plane and is appropriately counterweighted to swing a laterally open curved deflector spoon cyclically into interrupting engagement with the projected water stream. The water stream interacts with the deflector spoon to swing the spoon away from the stream and further to impart a lateral torque transmitted through the drive arm to the sprinkler body to rotate the sprinkler through a relatively small step, after which the drive arm returns the deflector spoon for subsequent water stream interruption and sprinkler rotation through a subsequent step. Accordingly, the deflector spoon interrupts the water stream in a cyclic fashion to rotate the sprinkler through a series of relatively small steps thereby correspondingly altering the direction of throw of the projected water stream. This stepwise movement can be allowed to continue through repeated full-circle rotations, or alternatively, if desired, a suitable reversing mechanism can be provided to reverse the direction of rotation within the limits of a preselected arcuate path.
Reaction drive water sprinklers of the type described have been used widely in agricultural irrigation systems requiring a relatively high flow water stream to be projected a substantial distance from the sprinkler. In this type of sprinkler, sometimes referred to as a large gun or big gun sprinkler, the deflector spoon interacts with the high energy water stream to drive the sprinkler in steps in one rotational direction. For part-circle operation, a reversing mechanism responds to sprinkler movement reaching one end limit of a selected arcuate path to move a reversing cam into interrupting engagement with the high energy stream. This results in a relatively high reaction force swinging the sprinkler rapidly back through the arcuate path to the other end limit whereupon the reversing cam is retracted from the water stream and normal stepwise rotation by means of the deflector spoon is resumed. Commercial examples of the foregoing type of reaction drive sprinkler are the Model 102 and Model 103 Rain Guns manufactured by Rain Bird Sprinkler Mfg. Corp. of Glendora, Calif. In such reversible reaction drive sprinklers, the provision of a reversing cam and related actuating components undesirably increases the overall cost and complexity of the sprinkler. Moreover, reversing cam engagement with the high energy water stream can cause extremely rapid reversed rotational movement which can in turn contribute to excessive component wear and/or failure of mechanical components. Still further, interruption of the high energy water stream by the deflector spoon and the reversing cam knocks down a portion of the stream thereby effectively reducing sprinkler range.
In U.S. Pat. No. 4,434,937, an improved reaction drive sprinkler is disclosed of the so-called large or big gun type. This improved reaction drive sprinkler includes a relatively large range tube through which a high flow, high energy water stream is projected a substantial distance from the sprinkler, together with a comparatively smaller drive nozzle through which a secondary, significantly lower energy water stream is projected for reversible driving purposes. This lower energy water stream is interrupted in a cyclic manner by one of a pair of oppositely curved deflector spoons carried on a pivoting reaction drive arm, with the drive nozzle being formed from a flexible rubber-based or plastic material movable to aim the lower energy stream for engagement with either deflector spoon in accordance with the desired direction of rotational sprinkler stepping movement. The flexible drive nozzle can thus be set to rotate the sprinkler stepwise through a full-circle path in either direction or the drive nozzle can be switched by a reversing mechanism back and forth to achieve reversible sprinkler stepwise rotation within the limits of a preselected arcuate path. While this use of the relatively low energy stream for driving purposes advantageously results in controlled sprinkler movement in both rotational directions together with reduced component wear, the flexible drive nozzle has not provided consistent drive performance particularly when subjected to varying operating parameters, such as temperature or pressure. For example, variations in these and other parameters can produce widely variant physical characteristics for the lower energy drive stream thereby resulting in unacceptably inconsistent reaction drive forces and sometimes making it difficult to aim the stream for proper interaction with the selected deflector spoon.
There exists, therefore, a significant need for an improved drive assembly for a reaction drive sprinkler of the general type described in U.S. Pat. No. 4,434,937, wherein the improved drive assembly includes means for providing a relatively low energy water stream having substantially consistent drive characteristics and wherein this water stream can be shifted accurately back and forth for controlled interruption by two oppositely oriented deflector spoons. The present invention fulfills these needs and provides further related advantages.